Regenerators are known having at each end several manifold collectors each secured to the respective ends of a respective group of tubes that are in turn each used for a respective fluid medium. Thus if two media are used, there will be two such manifold connectors at each end of the regenerator. The tubes generally run along the central axis of the regenerator and are welded or soldered at their ends to the respective manifold connectors.
Such a regenerator has the considerable disadvantage that the tubes of each group or bundle vary considerably in length. This is due to the fact that it is not possible to bring all of the tubes for a given medium out of the bundle at the same cylindrical height if they are to be manifolded together at one spot. These different tube lengths create different flow resistances in the different tubes of the bundle and therefore create different temperature differences. Thus only a few of the tubes of each bundle or group are connected directly at their ends to the manifold connectors. The temperature difference between the medium in the tubes and therearound is frequently relatively great.